• Journal of Yeungnam Medical Science
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• v.23 no.1
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• pp.71-81
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• 2006

Background: This study was done to better understand patterns, trends and local distribution patterns of malocclusion so that we can provide adequate information to patients, to help make the appropriate diagnosis and therapeutic plans, and to assess the future directions of malocclusion treatment. Materials and Methods: Malocclusion patterns, distribution and trends of visiting patients were examined in 993 malocclusion patients who had been evaluated and diagnosed at the Department of Dentistry, Yeungnam University Hospital over a 10-year period from 1995 to 2004. Results: The number of visiting patients per year showed an increasing trend and the visit rate was 1.28 time-higher in females(56.1%) than in males(43.9%). 1) Age distribution showed that the 7-12 year-old group was the largest (36.7%). Geographic distribution showed the majority of patients were from the Dalseo district(28.2%). Angle's malocclusion classification revealed that class III was the largest(38.4%). Crowding was the chief complaint in the highest percentage of patients(33.9%). The therapeutic method used was the fixed appliance in 61% of cases and a combination with extraction in 30.8%. Conclusions: The availability of dental services can accommodate orthodontic needs adequately as well as obtain reliable quantitative information regarding the characteristics of orthodontic patients.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.3
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• pp.111-122
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• 2021

Purpose: The purpose of this in vitro study was to investigate the flexural strength and translucency of three layers in 5Y-ZP and to assess the effect of additional firings on these properties. Materials and Methods: Sintered zirconia blocks were sectioned according to three layers : incisal, transition, and body. Disc-shaped specimens were fabricated from each layer. The diameter of specimens was 15.0 mm and each thickness of specimens for biaxial flexural strength test and translucency was 1.2 mm and 1.0 mm. The specimens were classified into subgroups according to the number of firing (0, 1, and 3 times; n = 10/subgroup) and the additional firings were performed under 900℃ using a furnace. Biaxial flexural strength and translucency was measured using universal testing machine and uv-vis spectrophotometer. X-ray diffraction (XRD) analysis was used for measurement of the phase identification. One-way ANOVA, Tukey HSD test were performed (α = 0.05). Results: There was no significant difference in flexural strength between the three layers (P > 0.05), while there was significant difference in translucency between different layers (P < 0.05). The flexural strength of incisal and transition layer was decreased by the single additional firing, and the three additional firings significantly decreased the flexural strength of three layers. The translucency of layer was decreased by additional firings except the body layer. The XRD patterns of all groups were similar. Conclusion: Three layers of 5Y-ZP were different only in translucency. Additional firings affected the flexural strength and translucency differently depending on the layers but crystalline phases were not changed.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.3
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• pp.123-129
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• 2021

Purpose: The purpose of this study was to investigate antifungal activity of shiitake mushroom yeast and hyphal type of Candida albicans. Materials and Methods: The extract from shiitake mushroom was collected by drying the supernatant after soaking shiitake mushrooms in water or ethanol. The antifungal activity of the extracts against yeast type of C. albicans was investigated by the susceptibility assay using microplate. C. albicans biofilm was formed on 12-well plate using Ham's F-12 medium in CO₂ incubator and treated with the ethanol extract. Furthermore, C. albicans biofilm was formed on denture base resin disk and treated with or without the ethanol extract in the presence of denture cleanser. Live C. albicans in biofilm was counted by cultured colony forming unit value after inoculated on agar plate. Results: Ethanol extract from shiitake mushroom showed stronger antifungal activity against yeast type of C. albicans compared to its water extract. The ethanol extract significantly reduced count of C. albicans in hyphal biofilm (P < 0.05). Also, the ethanol extract showed synergistically antifungal effect with denture cleanser on candidal biofilm on denture base resin disk (P < 0.05). Conclusion: The ethanol extract of shiitake mushroom may be a candidate for preventing candidal stomatitis as well as denture-related stomatitis.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.3
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• pp.101-110
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• 2021

Purpose: In this study, we intended to study the change in bond strength according to the thermal cycling of provisional resin and 3D printed resin for making provisional restoration. Materials and Methods: Through DLP method, 3D printed resin powder was used to produce 3D printed resin samples. The samples were grouped into eight groups, according to types of provisional resin (PMMA, bis-acryl resin) which is to be bonded on the samples and numbers of thermal cycling (control, 2,000, 3,000, 5,000 cycles). Shear bond strength of the bonded samples was measured on the universal testing machine. Results: As the number of thermal cycling increased, the shear bond strength of PMMA and bis-acryl resin for 3D printed resins decreased except between 3,000 cycles and 5,000 cycles in PMMA groups. In the PMMA group, there were significant differences in shear bond strength between less number than 3,000 cycles (P < 0.05) and no significant differences between more number than 3,000 cycles (P > 0.05). In the bis-acryl resin group, there were significant differences in shear bond strength between control and 2,000 cycles, control and 3,000 cycles, and control and 5,000 cycles (P < 0.05), no significant difference between 2,000 and 3,000 cycles, between 3,000 and 5,000 cycles (P > 0.05). Conclusion: The shear bond strength between 3D printed resin and provisional resin tended to decrease after thermal cycling.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.2
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• pp.81-89
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• 2019

Purpose: This study aimed to investigate the correlation between the solubility and the amount of fluoride release when a resin surface coating agent is applied to RMGIC. Materials and Methods: To measure the fluoride release and solubility, Fuji II $LC^{(R)}$and $Filtek^{TM}$ Z350XT without a surface coating, Fuji II $LC^{(R)}$ with G coat $plus^{TM}$ and Fuji II $LC^{(R)}$ with $Permaseal^{(R)}$ were prepared. And the amount of fluoride release and solubility were measured. Results: There was no significant difference in the daily fluoride release between the surface coating agents. The cumulative fluoride release was significantly different between the groups using RMGIC at 56 days (P < 0.05). In the solubility measurement, RMGIC without surface coating was significantly different only on the 7th day compared to the other three groups (P < 0.05). Conclusion: Surface coating agents can prevent the degradation of properties by the initial solvent in RMGIC. Therefore, fluoride is preserved inside the restorative material and the effect of surface coating after the addition is reduced, so that the effect on fluoride release and storage is also reduced.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.253-261
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• 2018

Purpose: The purpose of this study was to analyze correlation between bruxism and occlusal contacts on balancing side. Materials and Methods: The purpose of this study is to compare the difference of group function and balancing side occlusal contacts according to bruxism and sex, A total of 100 adults that aged 26-37 years (39 bruxers and 61 non-bruxers) were examined. The lateral excursion and balanced occlusal contacts were analyzed to determine the correlation with bruxism. The occlusal contacts were recorded by T-Scan system and articulating paper. Results: The group function was the highest in 61.5% of bruxers and 47.5% of non-bruxers. In comparison between males and females, group function was 58.9% in males and 37.0% in females. Occlusal contacts on non-working side occurred in 48 out of 100 patients. There were 51.2% of the cases in the bruxers and 46.0% in the non-bruxers. Statistically, there was no correlation between the bruxism and occlusal contacts on non-working side. There was no correlation between sex and balancing occlusal contacts. Conclusion: There was no significant correlation between bruxism and occlusal contacts on non-working side. The group function was the highest in bruxers when lateral excursion was occurred.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.262-269
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• 2018

Purpose: The purpose of this study was to evaluate the deformation of the complete denture artificial teeth arrangement after festooning over time. Materials and Methods: 10 wax dentures of equal teeth arrangement and equal gingival contour were used in this study. Festooning of the wax dentures were conducted and 3D model scans were conducted every 10 minutes for 120 minutes. Interdental transverse distances were measured with the scanned images. Statistical analyses were performed with SPSS Ver. 22. 0. Results: Interdental transverse distance between teeth varied from 0.0999 mm to 0.1787 mm. Mean rate of deformation showed statistically significant change between the 40 - 50 minute interval and 50 - 60 minute interval and between the 50 - 60 minute interval and 60 - 70 minute interval. No statistically significant change of the mean rate of deformation was observed later on. Conclusion: Monitoring of the interdental transverse distance for 120 minute after festooning have shown the deformation and displacment of the artificial teeth arrangement. From after the 60 - 70 minute interval after festooning, the mean deformation showed no statistically significant change of the mean rate of deformation was observed. Within the limitations of this in vitro study results suggest that the final occlusal adjustment in wax denture before complete denture curing should be proceeded at least 60 minutes later after festooning.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.219-224
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• 2019

Purpose: The image registration of radiographic image and digital surface data is essential in the computer-guided implant guide system. The purpose of this study was to examine the effects of using micro-screw on the working time and convenience of operators in the process of image matching for guided implant surgery. Materials and methods: A mandibular dental model was prepared in partial edentulism for Kennedy class I classification. Two micro-screws were placed on the each side of retromolar area. Radiographic and scan images were taken using computed-tomography and digital scanning. The images were superimposed by 12 operators in software in two different conditions: using remaining teeth image alone and using teeth and micro-screws images. Working time, operator convenience and satisfaction were obtained, and analyzed using the Mann-Whitney U test (${\alpha}=.05$). Results: The working time was not statistically different between image registration conditions (P>.05); however, operator convenience and satisfaction were higher in the teeth and micro-screw assisted condition than in the teeth-alone assisted condition (P<.001). Conclusion: The use of micro-screw for the image registration has no effect in working time reduction, but improves operator convenience and satisfaction.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.132-142
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• 2019

Purpose: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. Materials and Methods: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. Results: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. Conclusion: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.153-159
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• 2019

Purpose: Aims to analyze the occlusal wear patterns in maxillary posterior teeth with palatal side abfractions and study the association between occlusal force and abfractions. Materials and Methods: This study was conducted in a total of 308 teeth from 148 patients with palatal side abfractions in maxillary posterior teeth. The occlusal wears in maxillary premolars and molars with palatal side abfractions were classified and recorded. The classification was done by type of teeth, age, and gender, and in order to evaluate the statistical significance between groups, chi-square test was conducted (${\alpha}=0.05$). Results: Palatal side abfractions in maxillary posterior teeth were observed at the highest frequency in the 1st molars, and in all teeth with palatal side abfractions, more than one occlusal wear was observed. In classification by type of teeth, by age, and by gender, the occlusal wears in teeth with palatal side abfractions were observed at high frequency in cuspal inclined plane, central fossa, and marginal ridge, and there was a statistical significance (P < 0.05). Conclusion: Palatal side abfractions were observed at the highest frequency in maxillary 1st molars, and in all maxillary posterior teeth where palatal side abfractions were found, the occlusal wears were observed. And the occlusal wears were observed at high frequency in cuspal inclined plane, central fossa and marginal ridge. Such results show that abfraction is associated with occlusal force.